Field
The present invention relates to a fuel cell system.
Related Art
With regard to a polymer electrolyte fuel cell, hereinafter may be simply referred to as “fuel cell”, a large amount of water is produced inside of the fuel cell during power generation. For example, JP 2008-034309A, JP 2010-108757A and JP 2005-317264A disclose examples of the fuel cell systems. Such fuel cell systems perform a process of removing water remaining inside of the fuel cell and inside of the system by purging or the like at an operation stop time of the fuel cell system, in order to suppress deterioration of the startability caused by freezing of the remaining water in a low temperature environment such as subzero environment.
At the operation stop time of the fuel cell system, it is preferable to perform a purging process to sufficiently remove water remaining inside of auxiliary machines involved in the flows of reactive gases and off-gases, such as valves and pumps. In the case of purging in a low temperature environment, however, the remaining water is likely to be frozen inside of such auxiliary machines. This may cause the remaining water inside of the auxiliary machines not to be sufficiently removed.
In the fuel cell systems described in JP 2010-108757A and JP 2005-317264A, a purging process and a heating process are performed for valves such as back pressure valves, for the purpose of removing water adhering to the valves. In the techniques of JP 2010-108757A and JP 2005-317264A, however, the purging process and the heating process for the valves are preformed independently of and separately from the purging process for the fuel cell. This is likely to decrease the system efficiency. In the fuel cell system, there is accordingly still a room for further improvement with regard to the technique of suppressing water from remaining in the fuel cell and the auxiliary machine after a stop of operation.